Formal or literary term for 'son', used mainly in written language or formal contexts. In everyday speech, 息子 (むすこ) is the common word.
He succeeded the family as the eldest son.
rest; relaxation; relief
suffocation; choking; asphyxia
asthma
news; letter; contact · whereabouts; movements
(someone else's) son
interest (on a loan, deposit, etc.)
cessation; end; coming to an end
underhanded; unfair; sneaky · makeshift; stopgap; temporary
rest; repose
good health; well-being · averting misfortune; warding off disaster
daughter (of someone of high standing) · (another's) daughter
sigh (of grief, disappointment, etc.); lament
son (honorific)
my son; one's son
bated breath; silence from fear or awe
beloved son; dear son
breathing; breath
expiry; dying; death
armrest; elbow rest
your son
(someone's) son
deep sigh
interest expense; interest paid
The kanji 息 originally means 'breath' or 'life', but in this reading そく it is used in formal contexts to mean 'son', likely derived from classical Chinese usage.